Heat pump

ABSTRACT

A heat pump has an evaporator for evaporating water as a working liquid so as to produce a working vapor, the evaporation taking place at an evaporation pressure of less than 20 hPa. The working vapor is compressed to a working pressure of at least 25 hPa by a dynamic-type compressor so as to then be liquefied within a liquefier by direct contact with liquefier water. The heat pump is preferably an open system, wherein water present in the environment in the form of ground water, sea water, river water, lake water or brine is evaporated, and wherein water which has been liquefied again is fed to the evaporator, to the soil or to a water treatment plant.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/910,062 filed Oct. 22, 2010, which is a divisional of U.S. patentapplication Ser. No. 11/695,515, filed Apr. 2, 2007 (now U.S. Pat. No.7,841,201), which claims priority to U.S. Patent Application No.60/789,324, filed on Apr. 4, 2006, and from International PatentApplication No. PCT/EP2006/003061, also filed on Apr. 4, 2006, which areall incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to heat pumps, and in particular to heatpumps which may be employed for heating buildings, and specifically forheating relatively small building units, such as detached houses,semi-detached houses or row houses.

Description of the Prior Art

FIG. 8 shows a known heat pump as is described in “TechnischeThermodynamik”, Theoretische Grundlagen and praktische Anwendungen, 14threvised edition, Hanser Verlag, 2005, pp. 278-279. The heat pumpincludes a closed cycle, within which a working substance, such as R134a, circulates. Via a first heat exchanger 80 and the evaporator, somuch heat is withdrawn from the soil, or the ground water, that theworking substance evaporates. The working substance, which now is richin energy, is extracted by the compressor via the suction line. Withinthe compressor 81, it is/it will be compressed, thus increasing pressureand temperature. This compression is performed by a piston compressor.The working substance, which has been compressed and exhibits a hightemperature, now passes into the second heat exchanger 82, theliquefier. Within the liquefier, so much heat is withdrawn from theworking substance by the heating or process-water cycle that thecoolant, being subject to high pressure and high temperature, isliquefied. Within the choke or expansion member 83, the workingsubstance is expanded, i.e. the working substance is relieved of stress.Here, pressure and temperature are reduced to such an extent that theworking substance is again able to re-absorb energy from the soil or theground water within the evaporator. Now the cycle is complete and startsagain.

As can be seen from this, the working substance serves as an energytransporter so as to take up heat from the soil or ground water, and togive it off, within the liquefier, to the heating cycle. In this processmanagement, the 2nd law of thermodynamics is complied with, said lawstating that heat or energy only be transferred, “on its own”, can froma higher temperature level to a lower temperature level, and thatinversely this may also occur by means of energy supply from outside,here by the driving work of the compressor.

FIG. 7 shows a typical h, log p diagram (h is the enthalpy, p thepressure of a material). An isobaric evaporation of the workingsubstance takes place, between point 4 and point 1 in the diagram ofFIG. 7, at low values for the pressure and the temperature (p1, T1).Here, the heat Q81 is supplied.

Ideally, a reversible compression of the working substance vapor to apressure of p2 is performed, between point 1 and point 2, within anadiabatic compressor. The temperature rises to T2 in the process. A workof compression is to be supplied here.

Then, isobaric cooling of the working substance vapor from 2 to 2′ isperformed at a high pressure p2. Overheating is reduced. Subsequently,the working substance is liquefied. Overall, the heat Q25 can bedissipated.

Within choke 83, the working substance is choked, in an adiabaticmanner, from the high pressure p2 to the low pressure p1. In theprocess, part of the liquid working substance evaporates, and thetemperature falls to the evaporating temperature T1. In the h, log pdiagram, the energies and characteristics of this process may becalculated by means of enthalpies, and may be illustrated, as is shownin FIG. 7.

The working fluid of the heat pump thus takes up, within the evaporator,heat from the surroundings, i.e. air, water, waste water or the soil.The liquefier serves as a heat exchanger for heating up a heatingsubstance. Temperature T1 is slightly lower than the ambienttemperature, temperature T2 is considerably higher and temperature T2′slightly higher than the heating temperature necessary. The higher thetemperature difference called for, the more work must be effected by thecompressor. Therefore, it is desired to keep the rise in temperature assmall as possible.

Thus, with regard to FIG. 7, a compression of the working materialvapors is performed, in the ideal case, along the curve for the entropys=constant up to point 2. From here up to point 3, the working materialliquefies. The length of the distance 2-3 represents the useful heat Q.From point 3 to point 4, the working material is expanded, and frompoint 4 to point 1, it is evaporated, the distance 4-1 reflecting theheat withdrawn from the heat source. Unlike the T, s diagram, themagnitudes of the heat and of the work may be taken as distances in theh, log p diagram. Pressure losses within valves, within the pressure andsuction lines, of the compressor, etc. change the ideal curve of thecyclic process in the h, log p diagram and reduce the effectiveness ofthe entire process.

With piston compressors, the working material vapor which has beensucked in initially has a lower temperature than the cylinder wall ofthe compressor, and thus absorbs heat from it. As the compressionincreases, the temperature of the working material vapor eventuallyincreases to exceed that of the cylinder wall, so that the workingmaterial vapor gives off heat to the cylinder wall. Then, when thepiston again sucks in and compresses vapor, the temperature of thepiston wall is initially fallen below again and then exceeded, whichleads to constant losses. In addition, overheating of the workingmaterial vapor which has been sucked in will be called for and necessaryfor the compressor to no longer suck in any liquid working material.What is also disadvantageous, in particular, is the heat exchange withthe oil cycle of the piston compressor, which is indispensable forlubrication.

Any irreversible processes, such as heat losses during compression,pressure losses within the valves, and flow losses within the pressureline for liquefying and within the liquefier, will increase the entropy,i.e. the heat which cannot be retrieved. In addition, temperature T2,also exceeds the liquefying temperature. Such an “overheating enthalpy”is undesired, in particular because the high temperatures occurring inthe process will accelerate the aging of the compressor and, inparticular, of the lubricating oil within a piston compressor. Also, theeffectiveness of the process is reduced.

The liquefied working material at a low temperature at the output of theliquefier would have to be expanded, within the context of an idealcyclic process, via an engine, for example a turbine, so as to exploitthe excess energy which was present in comparison with the state presentat the temperature and the pressure prior to compressing. Because of thegreat expenditure necessary for this, this measure is dispensed with,and the pressure of the working material is abruptly reduced to the lowpressure and the low temperature by the choke 83. The enthalpy of theworking material remains approximately the same in the process. Due tothe abrupt pressure reduction, the working material must partiallyevaporate to reduce its temperature. The evaporation heat necessary isderived from the working material exhibiting excess temperature, i.e. isnot withdrawn from the heat source. The entirety of the losses caused bythe expansion within choke 83 (FIG. 8) is referred to as expansionlosses. These are exergy losses because heat of a temperature T isconverted to heat of a temperature T0. These losses may be reduced ifthe liquid working material can dissipate its heat to a medium having atemperature smaller than T. This undercooling enthalpy may be exploitedby an internal heat exchange which, however, also necessitatesadditional expenditure in terms of equipment. Also in principle, theinternal heat exchange has its limitation, because in the compression ofthe vapors, the overheating temperature T2 increases, whereby the gainsachieved are partly cancelled out, and because also more thermal strainis put on the machine and the lubricating oil. Eventually, theoverheating causes the volume of the vapor to increase, whereby thevolumetric heat power decreases. This heat is utilized for preheatingthose vapors of the working material which flow to the compressor, onlyto the extent necessary for being sure that all droplets contained inthe vapor of the working medium are converted to vapor.

In general, one may state that the ratio of the enthalpy differencebetween point 1 and point 4 and the enthalpy difference between point 2and point 1 of the h, log p diagram is a measure of the economicefficiency of the heat pump process.

A working substance which is currently popular is R134a, the chemicalformula of which is CF3-CH2F. It is a working substance which, eventhough it is no longer damaging to the ozone layer, nevertheless has animpact, in terms of the greenhouse effect, which is 1000 times higherthan that of carbon dioxide. However, the working substance R134a ispopular since it has a relatively large enthalpy difference of about 150kJ/kg.

Even though this working substance is no longer an “ozone killer”, thereare nevertheless considerable requirements placed upon the completenessof the heat pump cycle, to the effect that no molecules of the workingsubstance will escape from this closed cycle, since they would causeconsiderable damage due to the greenhouse effect. This encapsulationleads to considerable additional cost when building a heat pump.

Also, one must assume that by the time the next stage of the KyotoProtocol is implemented, R134a will be prohibited by the year 2015because of the greenhouse effect, which has also happened to previous,considerably more damaging substances.

What is therefore disadvantageous about existing heat pumps, beside thefact of the harmful working substance, is also the fact that, due to themany losses within the heat pump cycle, the efficiency factor of theheat pump typically does not exceed a factor of 3. In other words, 2times the energy that has been used for the compressor may be withdrawnfrom the heat source, such as the ground water or the soil. Whenconsidering heat pumps wherein the compressor is driven by electricalcurrent, and when considering, at the same time, that the efficiencyfactor in current generation is perhaps 40%, one will find that—withregard to the overall energy balance—the use of a heat pump is veryquestionable. In relation to the source of primary energy, 120%=3 □ 40%of heat energy are provided. A conventional heating system using aburner achieves efficiency factors of at least 90-95%, i.e. animprovement of only 25-30% is achieved at high technical and, therefore,financial expense.

Improved systems use primary energy for driving the compressor. Thus,gas or oil is burned to provide the compressor rating using the energyreleased by combustion. What is advantageous about this solution is thefact that the energy balance actually becomes more positive. The reasonfor this is that even though only about 30% of the source of primaryenergy may be used as driving energy, the waste heat of, in this case,about 70% can also be used for heating. The heating energy provided willthen amount to 160%=3 □30%+70% of the source of primary energy. What isdisadvantageous about this solution, however, is that a household willnevertheless necessitate a combustion engine and a fuel store eventhough it has no longer a classical heating system. The expenditure madefor engine and fuel storage must be added to the expense made for theheat pump, which, after all, is a highly closed cycle due to the coolantbeing harmful to the climate.

All of these things have resulted in that heat pumps have had onlylimited success in competition with other types of heating systems.

SUMMARY OF THE INVENTION

According to an embodiment, a heat pump may have: an evaporator forevaporating water as a working liquid to generate a working vapor, theevaporator having an evaporation chamber and being configured togenerate an evaporation pressure of less than 20 hPa within theevaporation chamber, so that the water will evaporate at temperaturesbelow 18° C.; a compressor coupled to the evaporator for compressing theworking vapor, the compressor being configured as a dynamic-typecompressor and further being configured to compress the working vapor toa working pressure of more than 5 hPa above the evaporation pressure;and a liquefier for liquefying a compressed working vapor, the liquefierbeing configured to output a heat which has been obtained during theliquefaction to a heating system.

According to another embodiment, an evaporator apparatus for a heat pumpmay have: a water evaporator for evaporating water as a working liquidto generate a working vapor, the evaporator having an evaporationchamber and being configured to generate an evaporation pressure of lessthan 20 hPa within the evaporation chamber, so that the water willevaporate at temperatures below 18° C.

According to another embodiment, a compressor/liquefier system for aheat pump having an evaporator for evaporating water as a working liquidso as to generate a working vapor having an evaporation pressure mayhave: a compressor coupled to the evaporator for compressing the workingvapor, the compressor being configured as a dynamic-type compressor andfurther being configured to compress the working vapor to a workingpressure of more than 5 hPa above the evaporation pressure; and aliquefier for liquefying a compressed working vapor, the liquefier beingconfigured to output a heat which has been obtained during theliquefaction to a heating system.

According to another embodiment, a method of pumping heat may have thesteps of: evaporating water as a working liquid to generate a workingvapor, the working vapor being generated at an evaporation pressure ofless than 20 hPa, so that the water will evaporate at temperatures below18° C.; compressing the working vapor in terms of flow so as to compressthe working vapor to a working pressure of more than 5 hPa above theevaporation pressure; and liquefying a compressed working vapor tooutput a heat which has been obtained during the liquefaction to aheating system.

According to another embodiment, a method of evaporating water within aheat pump may have the steps of: evaporating water as a working liquidto generate a working vapor, the working vapor being generated at anevaporation pressure of less than 20 hPa, so that the water willevaporate at temperatures below 18° C.

According to another embodiment, a method of compressing and liquefyingfor a heat pump having an evaporator for evaporating water as a workingliquid to produce a working vapor with an evaporation pressure may havethe steps of: compressing the working vapor in terms of flow so as tocompress the working vapor to a working pressure of more than 5 hPaabove the evaporation pressure; and liquefying a compressed workingvapor to output a heat which has been obtained during the liquefactionto a heating system.

According to another embodiment, a computer program may have a programcode for performing the method of pumping heat, the method having thesteps of: evaporating water as a working liquid to generate a workingvapor, the working vapor being generated at an evaporation pressure ofless than 20 hPa, so that the water will evaporate at temperatures below18° C.; compressing the working vapor in terms of flow so as to compressthe working vapor to a working pressure of more than 5 hPa above theevaporation pressure; and liquefying a compressed working vapor tooutput a heat which has been obtained during the liquefaction to aheating system, when the computer program runs on an arithmetic-logicunit.

According to another embodiment, a computer program may have a programcode for performing the method of pumping heat, the method having thesteps of: evaporating water as a working liquid to generate a workingvapor, the working vapor being generated at an evaporation pressure ofless than 20 hPa, so that the water will evaporate at temperatures below18° C., when the computer program runs on an arithmetic-logic unit.

According to another embodiment, a computer program may have a programcode for performing the method of compressing and liquefying for a heatpump having an evaporator for evaporating water as a working liquid toproduce a working vapor with an evaporation pressure, the method havingthe steps of: compressing the working vapor in terms of flow so as tocompress the working vapor to a working pressure of more than 5 hPaabove the evaporation pressure; and liquefying a compressed workingvapor to output a heat which has been obtained during the liquefactionto a heating system, when the computer program runs on anarithmetic-logic unit.

The present invention is based on the realization that one must get awayfrom working substances which are detrimental to the climate, and thatnormal water is an optimum working substance instead. In comparison withthe working substance R134a, which is frequently used these days, wateradditionally has a considerably larger ratio of the enthalpydifferences. The enthalpy difference, which is decisive in terms of howeffective the heat pump process is, amounts to about 2500 kJ/kg forwater, which is about 16 times as much as the usable enthalpy differenceof R134a. The compressor enthalpy to be expended, by contrast, is only4-6 times as large, depending on the operating point.

In addition, water is not harmful to the climate, i.e. is neither anozone killer, not does it aggravate the greenhouse effect. This enablesheat pumps to be built in a considerably simpler manner, since therequirements placed upon the completeness of the cycle are not high.Instead, it is even preferred to completely leave behind the closedprocess and to make an open process instead, wherein the ground water,or the water representing the exterior heat source, is directlyevaporated.

In accordance with the invention, the evaporator is configured such thatit comprises an evaporation chamber within which the evaporationpressure is lower than 20 hPa (hectopascal), so that water willevaporate at temperatures below 18° C. and, preferably, below 15° C. Inthe northern hemisphere, typical ground water has temperatures ofbetween 8 and 12° C., which necessitates pressures of below 20 hPa forthe ground water to evaporate, so as to be able to achieve, byevaporating the ground water, a reduction in the temperature of theground water and, thus, heat removal, by means of which a heating systemwithin a building, such as a floor heating system, may be operated.

In addition, water is advantageous in that water vapor takes up a verylarge volume, and in that it is no longer necessary to fall back on adisplacement machine such as a piston pump or the like in order tocompress the water vapor, but that a high-performance compressor in theform of a dynamic-type compressor, such as a radial-flow compressor, maybe employed which is highly controllable in terms of its technology andis cost-efficient in terms of its production since it exists in highquantities and has been used up to now as a small turbine or as aturbocompressor in cars, for example.

A prominent representative of the pedigree of dynamic-type compressorsas compared to displacement machines is the radial-flow compressor, forexample in the form of a turbocompressor comprising a radial-flow wheel.

The radial-flow compressor, or the dynamic-type compressor, must achieveat least such a level of compression that the output pressure exitingfrom the radial-flow compressor is at least 5 hPa higher than the inputpressure into the radial-flow compressor. Preferably, however, acompression will have a ratio larger than 1:2, and even larger than 1:3.

Compared to piston compressors, which are typically employed withinclosed cycles, dynamic-type compressors additionally have the advantagethat the compressor losses are highly reduced, due to the temperaturegradient existing within the dynamic-type compressor, as compared with adisplacement machine (piston compressor), wherein such a stationarytemperature gradient does not exist. What is particularly advantageousis that an oil cycle is completely dispensed with.

Moreover, particular preference is given to multi-stage dynamic-typecompressors to achieve the relatively high level of compression whichshould have a factor of 8 to 10 in order to achieve sufficient advanceflow temperature in a heating system even for cold winter days.

In a preferred embodiment, a fully open cycle is employed, wherein theground water is made to have the low pressure. A preferred embodimentfor generating a pressure below 20 hPa for ground water consists in thesimple use of a riser pipe leading to a pressure-tight evaporationchamber. If the riser pipe overcomes a height of between 9 and 10 m, theevaporation chamber will comprise the low pressure necessary at whichthe ground water will evaporate at a temperature of between 7 and 12° C.Since typical buildings are at least 6 to 8 m in height and since inmany regions, the ground water is present already at 2 to 4 m below thesurface of the earth, installing such a pipe leads to no considerableadditional expense since it is only necessary to dig a little deeperthan for the foundations of the house, and since typical heights ofbuildings are readily high enough for the riser pipe or the evaporationchamber not to protrude above the building.

For cases of application wherein only a shorter riser pipe is possible,the length of the riser pipe may be readily reduced by a pump/turbinecombination which only necessitates a minor amount of additional workfrom the outside due to the fact that the turbine is used for convertingthe high pressure to the low pressure, and the pump is used forconverting the low pressure to the high pressure.

Thus, primary heat-exchanger losses are eliminated, since no primaryheat exchanger is used but use is made of the evaporated ground waterdirectly as a working vapor or a working substance.

In a preferred embodiment, no heat exchanger is used even in theliquefier. Instead, the water vapor which is heated up due to beingcompressed is directly fed into the heating-system water within aliquefier, so that within the water, a liquefaction of the water vaportakes place such that even secondary heat-exchanger losses areeliminated.

The inventive water evaporator/dynamic-type compressor/liquefiercombination thus enables efficiency factors of at least 6 in comparisonwith common heat pumps. Thus, it is possible to withdraw from the groundwater at least 5 times the amount of the electric energy spent forcompression, so that a heating energy of 240%=6 □40%, in relation to thesource of primary energy, is provided even if the dynamic-typecompressor is operated with electrical current. As compared with theart, this represents at least double the efficiency or half of theenergy costs. This is particularly true for the emission of carbondioxide, which is relevant in terms of the climate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1a is a basic block diagram of the inventive heat pump;

FIG. 1b is a table for illustrating various pressures and theevaporation temperatures associated with these pressures;

FIG. 2 is a block diagram of a preferred embodiment of the inventiveheat pump operated with ground water, sea water, river water, lake wateror brine;

FIG. 3a is an alternative embodiment of the liquefier of FIG. 2;

FIG. 3b is an alternative embodiment of the liquefier with a reducedbackflow in the off operation;

FIG. 3c is a schematic representation of the liquefier having a gasseparator;

FIG. 4a is a preferred implementation of the evaporator of FIG. 2;

FIG. 4b is an alternative embodiment of the evaporator using theliquefier drain as a boiling assistance;

FIG. 4c is an alternative embodiment of the evaporator having a heatexchanger for using ground water for boiling assistance;

FIG. 4d is an alternative embodiment of the evaporator comprisingfeeding from the side and draining in the center;

FIG. 4e is a schematic representation of the expander with an indicationof preferred measurements;

FIG. 5a is an alternative implementation of the evaporator for reducingthe height of the riser pipe;

FIG. 5b is an implementation of an alternative realization of connectinga heating line to the liquefier with a turbine/pump combination;

FIG. 6a is a schematic representation of the compressor performed byseveral dynamic-type compressors arranged one behind the other;

FIG. 6b is a schematic representation of the setting of the numbers ofrevolutions of two cascaded dynamic-type compressors as a function ofthe target temperature;

FIG. 6c is a schematic top view of a radial-flow wheel of a dynamic-typecompressor in accordance with a preferred embodiment of the presentinvention;

FIG. 6d is a schematic cross-sectional view with a merely schematicalrepresentation of the radial-wheel vanes for illustrating the differentexpansions of the vanes with regard to the radius of the radial-flowwheel;

FIG. 7 is an exemplary h, log p diagram; and

FIG. 8 is a known heat pump performing the left-handed cycle of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1a shows an inventive heat pump which initially comprises a waterevaporator 10 for evaporating water as a working fluid so as togenerate, on the output side, a vapor within a working vapor line 12.The evaporator includes an evaporation chamber (not shown in FIG. 1a )and is configured to generate, within the evaporation chamber, anevaporation pressure lower than 20 hPa, so that the water will evaporatewithin the evaporation chamber at temperatures below 15° C. The water ispreferably ground water, brine circulating freely within the soil orwithin collector pipes, i.e. water with a specific salt content, riverwater, lake water or sea water. In accordance with the invention, alltypes of water, i.e. limy water, non-limy water, saline water ornon-saline water, are preferably used. This is due to the fact that alltypes of water, i.e. all of these “water materials”, have the favorableproperty of water, i.e. consisting in that water, also known as “R 718”,has an enthalpy-difference ratio of 6 usable for the heat pump process,which corresponds to more than double a typically usableenthalpy-difference ratio of, e.g., R134a.

The water vapor is fed, by suction line 12, to a compressor/liquefiersystem 14 comprising a dynamic-type compressor, such as a radial-flowcompressor, for example in the form of a turbocompressor designated by16 in FIG. 1a . The dynamic-type compressor is configured to compressthe working vapor to a vapor pressure of at least more than 25 hPa. 25hPa correspond to a liquefying temperature of about 22° C., which mayalready be a sufficient heating-system advance flow temperature of afloor heating system, at least on relatively warm days. In order togenerate higher advance flow temperatures, pressures of more than 30 hPamay be generated using dynamic-type compressor 16, a pressure of 30 hPahaving a liquefying temperature of 24° C., a pressure of 60 hPa having aliquefying temperature of 36° C., and a pressure of 100 hPacorresponding to a liquefying temperature of 45° C. Floor heatingsystems are designed to be able to provide sufficient heating with anadvance flow temperature of 45° C. even on very cold days.

The dynamic-type compressor is coupled to a liquefier 18 which isconfigured to liquefy the compressed working vapor. By the liquefaction,the energy contained within the working vapor is fed to the liquefier 18so as to be fed to a heating system via the advance flow 20 a. Viabackflow 20 b, the working fluid flows back into the liquefier.

In accordance with the invention, it is preferred to extract the heat(heat energy) from the high-energy water vapor directly by the colderheating water, said heat (heat energy) being taken up by theheating-system water so that the latter heats up. In the process, somuch energy is extracted from the vapor that same becomes liquefied andalso participates in the heating cycle.

Thus, a loading of material into the liquefier, or the heating system,takes place, the loading being regulated by a drain 22, such that theliquefier in its liquefaction chamber has a water level which remainsbelow a maximum level despite the constant supply of water vapor and,thereby, of condensate.

As has already been explained, it is preferred to take an open cycle,i.e. to evaporate the water, which represents the heat source, directlywithout a heat exchanger. Alternatively, however, the water to beevaporated could also initially be heated up by an external heat sourcevia a heat exchanger. However, what is to be taken into account in thiscontext is that this heat exchanger again signifies losses andexpenditure in terms of apparatus.

In addition, it is preferred, in order to avoid losses for the secondheat exchanger which has been necessarily present so far on theliquefier side, to use the medium directly even there, i.e. to let thewater, which comes from the evaporator, circulate directly within thefloor heating system, when considering a house comprising a floorheating system.

Alternatively, however, a heat exchanger may be arranged, on theliquefier side, which is fed with the advance flow 20 a and whichcomprises the backflow 20 b, this heat exchanger cooling the waterpresent within the liquefier, and thus heating up a separate floorheating liquid which will typically be water.

Due to the fact that the working medium used is water, and due to thefact that only the evaporated portion of the ground water is fed intothe dynamic-type compressor, the degree of purity of the water isirrelevant. Just like the liquefier and, as the situation may be, thedirectly coupled floor heating system, the dynamic-type compressor isprovided with distilled water such that, in comparison with present-daysystems, the system has a reduced maintenance expenditure. In otherwords, the system is self-cleaning, since the system is only ever fedwith distilled water, and since the water within the drain 22 is thusnot contaminated.

In addition, it shall be noted that dynamic-type compressors have theproperties that—similar to a turbine of an airplane—they do not contactthe compressed medium with problematic materials such as oil. Instead,the water vapor is compressed only by the turbine or theturbocompressor, but is not contacted with oil or any other mediumnegatively affecting its purity, and thus is not contaminated.

The distilled water dissipated through the drain may thus be readilyre-fed to the ground water—if no other regulations are in the way.Alternatively, however, it may also be made to seep away, e.g. in thegarden or in an open area, or it may be fed to a waste waterpurification plant via the sewage system, if the regulations permit.

The inventive combination of water as a working substance with theuseful enthalpy-difference ratio which is doubly improved as comparedwith R134a, and due to the consequently reduced requirements placed uponthe closed nature of the system (rather, an open system is preferred)and due to the use of the dynamic-type compressor, by means of which thenecessary compression factors are efficiently achieved without anynegative effects on the purity, an efficient heat pump process which isneutral in terms of environmental damage is provided which will becomeeven more efficient if the water vapor is directly liquefied within theliquefier, since, in this case, not one single heat exchanger will benecessary in the entire heat pump process.

In addition, any losses associated with the piston compression aredispensed with. In addition, the losses, which are very low in the caseof water and which otherwise occur in the choking, may be used toimprove the evaporation process, since the drain water having the draintemperature, which will typically be higher than the ground watertemperature, is advantageously used to trigger a bubble evaporationwithin the evaporator by means of a structuring 206 of a drain pipe 204,as will be explained in FIG. 4a , in order to increase the evaporationefficiency.

A preferred embodiment of the present invention will be explained belowin detail with reference to FIG. 2. The water evaporator comprises anevaporation chamber 100 and a riser pipe 102, wherein ground water froma ground water reservoir 104 moves upward into the evaporation chamber100 in the direction of an arrow 106. The riser pipe 102 leads to anexpander 108 configured to expand the relatively narrow pipecross-section so as to provide as large an evaporation area as possible.The expander 108 will have the shape of a funnel, i.e. the shape of arotation paraboloid of any configuration. It may have round or squaretransitions. The only thing that is critical is that the cross-sectiondirected into the evaporation chamber 100, or the area facing theevaporation chamber 100, is larger than the cross-sectional area of theriser pipe so as to improve the evaporation process. If one assumes thatabout 1 l per second flows upward into the evaporation chamber throughthe riser pipe, about 4 ml per second are evaporated within theevaporator at a heating power of about 10 kW. The remainder exits,cooled by about 2.5° C., via the expander 108 and ends up in acontainment collection basin 110 within the evaporation chamber. Thecontainment collection basin 110 comprises a drain 112, within which thequantity of 1 l per second, minus the evaporated 4 ml per second, isdissipated again, preferably back to the ground water reservoir 104. Forthis purpose, a pump 114 or a valve for overflow control is provided. Itshall be noted that no active pumping is to be performed, since, due togravity, water will flow downward from the evaporator containment basin110 into the ground water reservoir via a backflow pipe 113 if the pumpof the valve 114 is opened. The pump or the valve 114 thus ensures thatthe water level within the containment basin does not rise to too high alevel or that no water vapor enters into the drain pipe 112, and thatthe evaporation chamber is also securely decoupled from the situation atthe “lower” end of the backflow pipe 113.

The riser pipe is arranged within a riser pipe basin 116 which is filledwith water by a pump 118 which is preferably provided. The levels in 116and 108 are connected to one another in accordance with the principle ofthe communicating pipes, gravity and the different pressures within 116and 108 ensuring that the water is transported from 116 to 108. Thewater level present in the riser pipe basin 116 is preferably arrangedsuch that, even with different air pressures, the level will never fallbelow the inlet of the riser pipe 102 so as to prevent air fromentering.

Preferably, evaporator 10 comprises a gas separator configured to removeat least part, e.g. at least 50% of a gas dissolved in the water to beevaporated, from the water to be evaporated, so that the removed part ofthe gas will not be sucked in by the compressor via the evaporationchamber. Preferably, the gas separator is arranged to feed the removedpart of the gas to a non-evaporated water so that the gas is transportedoff by the non-evaporated water. Dissolved gases may be oxygen, carbondioxide, nitrogen, etc. These gases evaporate mostly at a higherpressure than water does, so that the gas separator may be arrangeddownstream from the expander 108, so that oxygen etc., which has beenevaporated within the gas separator, will exit from the water which hasjust not been evaporated yet, and will preferably be fed into the returnpipe 113. Feeding-in is preferably performed at that location of thereturn pipe 113 at which the pressure is so low that the gas is againtaken along into the ground water by the back-flowing water.Alternatively, the separated gas may also be collected and be disposedof at specific intervals or be constantly vented, i.e. released to theatmosphere.

Typically, the ground water, sea water, river water, lake water, thebrine or any other naturally occurring aqueous solution will have atemperature of between 8° C. and 12° C. By lowering the temperature of 1l of water by 1° C., a power of 4.2 kW may be generated. If the water iscooled by 2.5° C., a power of 10.5 kW is generated. Preferably, acurrent of water with a current intensity depending on the heat power,in the example one liter per second, flows through the riser pipe.

If the heat pump works at a relatively high load, the evaporator willevaporate about 6 ml per second, which corresponds to a vapor volume ofabout 1.2 cubic meters per second. Depending on the heating-system watertemperature called for, the dynamic-type compressor is controlled withregard to its compression power. If a heating advance flow temperatureof 45° C. is desired, which is largely sufficient even for extremelycold days, the dynamic-type compressor will have to increase thepressure, which may have been generated at 10 hPa, to a pressure of 100hPa. If, on the other hand, an advance flow temperature of, e.g., 25° issufficient for the floor heating system, the compression that must beeffected by the dynamic-type compressor only will have a factor of 3.

The power generated is thus determined by the compressor rating, i.e.,on the one hand, by the compression factor, i.e. the degree to which thecompressor compresses and, on the other hand, by the volume flowgenerated by the compressor. If the volume flow increases, theevaporator will have to evaporate more, the pump 118 transporting moreground water into the riser pipe basin 116, so that more ground water isfed to the evaporation chamber. On the other hand, if the dynamic-typecompressor provides a lower compression factor, less ground water willflow from the bottom to the top.

However, it shall also be noted here that it is preferred to control thepassage of ground water through the pump 118. According to the principleof the communicating pipes, the filling level within container 116, orthe displacement capacity of the pump 118, establishes the amount offlow through the riser pipe. Therefore, an increase in the efficiency ofthe plant may be achieved, since the control of the flow is decoupledfrom the suction power of the dynamic-type compressor.

No pump is necessary for pumping the ground water from below into theevaporation chamber 100. Rather, this occurs “by itself”. This automaticrise up to the evacuated evaporation chamber also assists the fact thatthe negative pressure of 20 hPa may be readily achieved. No evacuationpumps or the like are necessary for this purpose. Rather, only a riserpipe having a height of more than 9 m is necessary. Then a purelypassive negative-pressure generation is achieved. However, the negativepressure necessary may also be generated using a considerably shorterriser pipe, for example when the implementation of FIG. 5a is employed.In FIG. 5a , a considerably shorter “riser pipe” is shown. Convertinghigh pressure to the negative pressure is accomplished via a turbine150, the turbine withdrawing energy from the working medium in thiscontext. At the same time, the negative pressure on the backflow side isagain returned to the high pressure, the energy necessary for this beingsupplied by a pump 152. The pump 152 and the turbine 150 are coupled toone another via a force coupling 154, so that the turbine drives thepump, specifically using the energy that the turbine has withdrawn fromthe medium. A motor 156 is merely still necessary for compensating forthe losses which the system inevitably will have, and to achieve thecirculation, i.e. to bring a system from its resting position into thedynamic mode depicted in FIG. 5 a.

In the preferred embodiment, the dynamic-type compressor is configuredas a radial-flow compressor with a rotatable wheel, it being possiblefor the wheel to be a slow-speed radial-flow wheel, a medium-speedradial-flow wheel, a half-axial flow wheel or an axial flow wheel, or apropeller, as are known in the art. Radial-flow compressors aredescribed in “Strömungsmaschinen”, C. Pfleiderer, H. Petermann,Springer-Verlag, 2005, pp. 82 and 83. Thus, such radial-flow compressorscomprise, as the rotatable wheel, the so-called center runner, the formof which depends on the individual requirements. Generally, anydynamic-type compressors may be employed, as are known asturbocompressors, fans, blowers or turbocondensers.

In the preferred embodiment of the present invention, radial-flowcompressor 16 is configured as several independent dynamic-typecompressors which may be controlled independently at least with regardto their number of revolutions, so that two dynamic-type compressors mayhave different numbers of revolutions. Such an implementation isdepicted in FIG. 6a , wherein the compressor is configured as a cascadeof n dynamic-type compressors. At various locations downstream from thefirst dynamic-type compressor, provision is preferably made of one oreven more heat exchangers, for example for heating processed water,which are designated by 170. These heat exchangers are configured tocool the gas which has been heated up (and compressed) by a precedingdynamic-type compressor 172. Here, overheating enthalpy is sensiblyexploited to increase the efficiency factor of the entire compressionprocess. The cooled gas is then compressed further using one or severaldownstream compressors, or is directly fed to the liquefier. Heat isextracted from the compressed water vapor for heating, e.g., processedwater to higher temperatures than, e.g., 40° C. However, this does notreduce the overall efficiency factor of the heat pump, but evenincreases it, since two successively connected dynamic-type compressorswith gas cooling connected in between, having a longer useful lifeachieve the necessary gas pressure within the liquefier due to thereduced thermal load and while needing less energy than if a singledynamic-type compressor without gas cooling were present.

The cascaded dynamic-type compressors operated independently arepreferably controlled by a controller 250 which maintains, on the inputside, a target temperature within the heating circuit and, as thesituation may be, also an actual temperature within the heating circuit.Depending on the target temperature desired, the number of revolutionsof a dynamic-type compressor which is arranged upstream in the cascadeand is referred to by n1, by way of example, and the number ofrevolutions n2 of a dynamic-type compressor which is arranged downstreamin the cascade are changed such as is depicted by FIG. 6b . If a highertarget temperature is input into the controller 250, both numbers ofrevolutions are increased. However, the number of revolutions of thedynamic-type compressor arranged upstream, which is referred to by n1 inFIG. 6b , is increased with a smaller gradient than the number ofrevolutions n2 of a dynamic-type compressor arranged downstream in thecascade. This results in that—when the ratio n2/n1 of the two numbers ofrevolutions is plotted—a straight line having a positive slope resultsin the diagram of FIG. 6 b.

The point of intersection between the numbers of revolutions n1 and n2which are individually plotted may occur at any point, i.e. at anytarget temperature, or may not occur, as the case may be. However, it isgenerally preferred to increase a dynamic-type compressor arrangedcloser to the liquefier within the cascade more highly, with regard toits number of revolutions, than a dynamic-type compressor arrangedupstream in the cascade, should a higher target temperature be desired.

The reason for this is that the dynamic-type compressor arrangeddownstream in the cascade must process further already compressed gaswhich has been compressed by a dynamic-type compressor arranged upstreamin the cascade. In addition, this ensures that the vane angle of vanesof a radial-flow wheel, as is also discussed with reference to FIGS. 6cand 6d , is positioned as favorably as possible with regard to the speedof the gas to be compressed. Thus, the setting of the vane angle onlyconsists in optimizing a compression of the in-flowing gas which is aslow in eddies as possible. The further parameters of the angle setting,such as gas throughput and compression ratio, which otherwise would haveenabled a technical compromise in the selection of the vane angle, andthus would have enabled an optimum efficiency factor at a targettemperature only, are brought, in accordance with the invention, to theoptimum operating point by the independent revolutions control, andtherefore have no longer any influence on the selection of the vaneangle. Thus, an optimum efficiency factor results despite an fixedly setvane angle.

In this regard, it is preferred, in addition, for a dynamic-typecompressor which is arranged more in the direction of the liquefierwithin the cascade to have a rotational direction of the radial-flowwheel which is opposed to the rotational direction of the radial-flowwheel arranged upstream in the cascade. Thus, an almost optimum entryangle of the vanes of both axial flow wheels in the gas stream may beachieved, such that a favorable efficiency factor of the cascade ofdynamic-type compressors occurs not only within a small targettemperature range, but within a considerably broader target temperaturerange of between 20 and 50 degrees, which is an optimum range fortypical heating applications. The inventive revolutions control and, asthe case may be, the use of counter-rotating axial flow wheels thusprovides an optimum match between the variable gas stream at a changingtarget temperature, on the one hand, and the fixed vane angles of theaxial flow wheels, on the other hand.

In preferred embodiments of the present invention, at least one orpreferably all of the axial flow wheels of all dynamic-type compressorsare made of plastic having a tensile strength of more than 80 MPa. Apreferred plastic for this purpose is polyamide 6.6 with inlaid carbonfibers. This plastic has the advantage of having a high tensilestrength, so that axial flow wheels of the dynamic-type compressors maybe produced from this plastic and may nevertheless be operated at highnumbers of revolutions.

Preferably, axial flow wheels are employed in accordance with theinvention, as are shown, for example, at reference numeral 260 in FIG.6c . FIG. 6c depicts a schematic top view of such a radial-flow wheel,while FIG. 6d depicts a schematic cross-sectional view of such aradial-flow wheel. As is known in the art, a radial-flow wheel comprisesseveral vanes 262 extending from the inside to the outside. The vanesfully extend toward the outside, with regard to axis 264 of theradial-flow wheel, from a distance of a central axis 264, the distancebeing designated by rW. In particular, the radial-flow wheel includes abase 266 as well as a cover 268 directed toward the suction pipe ortoward a compressor of an earlier stage. The radial-flow wheel includesa suction opening designated by r1 to suck in gas, this gas subsequentlybeing laterally output by the radial-flow wheel, as is indicated at 270in FIG. 6 d.

When looking at FIG. 6c , the gas in the rotational direction beforefrom the vane 262 has a higher relative speed, while it has a reducedspeed behind from the vane 262. However, for high efficiency and a highefficiency factor it is preferred for the gas to be laterally ejectedfrom the radial-flow wheel, i.e. at 270 in FIG. 6d , everywhere with asuniform a speed as possible. For this purpose, it is desirable to mountthe vanes 262 as tightly as possible.

For technical reasons, however, it is not possible to mount vanes whichextend from the inside, i.e. from the radius rW, to the outside astightly as possible, since the suction opening having the radius r1 thenwill become more and more blocked.

It is therefore preferred, in accordance with the invention, to providevanes 272 and 274 and 276, respectively, which extend over less than thelength of vane 262. In particular, the vanes 272 do not extend from rWfully to the outside, but from R1 to the exterior with regard to theradial-flow wheel, R1 being larger than rW. By analogy therewith, as isdepicted by way of example in FIG. 6c , vanes 274 only extend from R2 tothe exterior, whereas vanes 276 extend only from R3 to the outside, R2being larger than R1, and R3 being larger than R2.

These ratios are schematically depicted in FIG. 6d , a double hatching,for example within area 278 in FIG. 6d , indicating that there are twovanes in this area which overlap and are therefore marked by thedouble-hatched area. For example, the hatching from the bottom left tothe top right, shown in area 278, designates a vane 262 extending fromrW to the very outside, whereas the hatching extending from the top leftto the bottom right in area 278 indicates a vane 272 which extends onlyfrom r1 to the outside in relation to the radial-flow wheel.

Thus, at least one vane is preferably arranged between two vanesextending further to the inside, said one vane not extending so fartoward the inside. This results in that the suction area is not plugged,and/or that areas having a smaller radius are not too heavily populatedwith vanes, whereas areas having a larger radius are more denselypopulated with vanes, so that the speed distribution of the exiting gaswhich exists at the output of the radial-flow wheel, i.e. where thecompressed gas leaves the radial-flow wheel, is as homogeneous aspossible. With the inventive preferred radial-flow wheel in FIG. 6c ,the speed distribution of the exiting gas is particularly homogeneous atthe outer periphery, since the distance of vanes accelerating the gasand due to the “stacked” arrangement of the vanes is considerablysmaller than in a case where, for example, only vanes 262 are presentwhich extend from the very inside to the very outside, and thusnecessarily have a very large distance at the outer end of theradial-flow wheel, the distance being considerably larger than in theinventive radial-flow wheel as is depicted in FIG. 6 c.

It shall be noted at this point that the relatively expensive andcomplicated shape of the radial-flow wheel in FIG. 6c may be produced ina particularly favorable manner by plastic injection molding, it beingpossible, in particular, to simply achieve that all vanes, including thevanes which do not extend from the very inside to the very outside, i.e.vanes 272, 274, 276, are fixedly anchored, since they are connected bothto the cover 268 and to the base 266 of FIG. 6d . The use of plastic inparticular with the plastic injection molding technique enablesproduction of any shapes desired in a precise manner and at low cost,which is not readily possible or is possible only at very high expense,or is possibly not even possible at all, with axial flow wheels made ofmetal.

It shall be noted at this point that very high numbers of revolutions ofthe radial-flow wheel are preferred, so that the acceleration actingupon the vanes takes on quite considerable values. For this reason it ispreferred that particularly the shorter vanes 272, 274, 276 be fixedlyconnected not only to the base but also to the cover, such that theradial-flow wheel may readily withstand the accelerations occurring.

It shall also be noted in this context that the use of plastic isfavorable also because of the superior impact strength of plastic. Forexample, it cannot be ruled out that ice crystals or water droplets willhit the radial-flow wheel at least of the first compressor stage. Due tothe large accelerations, very large impact forces result here whichplastics having sufficient impact strength readily withstand. Inaddition, the liquefaction within the liquefier preferably occurs on thebasis of the cavitation principle. Here, small vapor bubbles collapse,on the basis of this principle, within a volume of water. From amicroscopic point of view, quite considerable speeds and forces arisethere which may lead to material fatigue in the long run, but which canbe readily controlled when using a plastic having sufficient impactstrength.

The compressed gas output by the last compressor 174, i.e. thecompressed water vapor, is then fed to the liquefier 18 which may beconfigured such as is depicted in FIG. 2, but which is preferablyconfigured such as is shown in FIG. 3a . The liquefier 18 containsvolume of water 180 and preferably a volume of steam 182 which may be assmall as is desired. The liquefier 18 is configured to feed thecompressed vapor into the water of the water volume 180, so that acondensation immediately results where the steam enters into the liquid,as is schematically drawn at 184. To this end, it is preferred for thegas supply to have an expansion area 186, such that the gas isdistributed over as large an area as possible within the liquefier watervolume 180. Typically, because of the temperature layers, the highesttemperature within a water tank will be at the top, and the coolesttemperature will be at the bottom. Therefore, the heating advance flowwill be arranged, via a floater 188, as close to the surface of thewater volume 180 as possible so as to extract the warmest water from theliquefier water volume 180. The heating backflow is fed to the liquefierat the bottom, so that the vapor to be liquefied comes in contact withwater which is as cool as possible and which moves, due to thecirculation using a heating circulating pump 312, again from the bottomin the direction of the steam-water border of the expander 186.

The embodiment in FIG. 2, wherein only a simple circulating pump 312exists, is sufficient when the liquefier is arranged in a building suchthat the areas to be heated are located below the liquefier, so that,due to gravitation, all heating pipes have a pressure which is largerthan that in the liquefier.

By contrast, FIG. 5b shows an implementation of a connection of aheating line to the liquefier having a turbine/pump combination if theliquefier is to be arranged at a height lower than that of the heatingline, or if a conventional heating which necessitates a higher pressureis to be connected. Thus, if the liquefier is to be arranged at a lowerheight, i.e. below an area to be heated, and/or below the heating line300, the pump 312 will be configured as a driven pump as is shown at 312in FIG. 5b . In addition, a turbine 310 will be provided within theheating backflow 20 b for driving the pump 312, the turbine 310 beingwired to the pump 312 via a force coupling 314. The high pressure willthen be present within the heating system, and the low pressure will bepresent within the liquefier.

Since the water level within the liquefier would rise more and more dueto the vapor being constantly introduced into the liquefier, the drain22 is provided, via which, e.g., about 4 ml per second must also drainoff for the water level within the liquefier to essentially not change.To this end, a drain pump, or a drain valve, 192 for pressure regulationis provided, such that without pressure loss, the necessary amount of,e.g., 4 ml per second, i.e. the quantity of water vapor which is fed tothe liquefier while the compressor is running, is drained off again.Depending on the implementation, the drain may be introduced into theriser pipe as is shown at 194. Since all kinds of pressures between onebar and the pressure existing within the evaporation chamber are presentalong the riser pipe 102, it is preferred to feed in the drain 22 intothe riser pipe at that location 194 where roughly the same pressureexists as it exists downstream from the pump 192, or valve 192. Then, nowork has to be done to re-feed the drain water to the riser pipe.

In the embodiment shown in FIG. 2, one operates completely without anyheat exchanger. The ground water is thus evaporated, the vapor is thenliquefied within the liquefier, and the liquefied vapor is eventuallypumped through the heating system and re-fed to the riser pipe. However,since only a (very small) part of, rather than all of, the quantity ofwater flowing through the riser pipe is evaporated, water which hasflown through the floor heating system is thus fed to the ground water.If something like this is prohibited according to communal regulations,even though the present invention entails no contamination whatsoever,the drain may also be configured to feed the amount of 4 ml per second,which corresponds to roughly 345 l per day, to the sewage system. Thiswould ensure that no medium which has been present within any heatingsystem of any building is directly fed back into the ground water.

However, the backflow 112 from the evaporator may be fed to the groundwater without any problems, since the water flowing back there only wasin contact with the riser pipe and the return line, but has not exceededthe “evaporation boundary” between the evaporation expander 108 and theoutput to the dynamic-type compressor.

It shall be noted that in the embodiment shown in FIG. 2, theevaporation chamber as well as the liquefier, or the vapor chamber 182of the liquefier, must be sealed off. As soon as the pressure within theevaporation chamber exceeds the mark necessary for the water beingpumped through the riser pipe to evaporate, the heat pump process comesto a “standstill”.

In the following, reference shall be made to FIG. 3a which represents apreferred embodiment of the liquefier 18. The feed line 198 forcompressed vapor is positioned within the liquefier such that the vapormay exit into this water volume just below the surface of the liquefierwater volume 180. For this purpose, the end of the vapor supply linecomprises nozzles arranged around the circumference of the pipe, throughwhich the vapor may exit into the water. For the mixing which occurs tobe as thorough as possible, i.e. for the vapor to come into contact withwater as cold as possible to liquefy as fast and efficiently aspossible, an expander 200 is provided. This expansion is arranged withinthe liquefier water volume 180. At its narrowest point, it has acirculating pump 202 configured to suck in cold water at the bottom ofthe liquefier and to displace it, by means of the expander, toward aflow which is directed upward and becomes broader. This is intended tocause as large quantities as possible of the vapor entering into theliquefier water 180 to contact water which is provided by thecirculating pump 202 and is as cold as possible.

In addition, it is preferred to provide, around the liquefier, a soundinsulation 208 which may be configured in an active or a passive manner.A passive sound insulation will insulate the frequencies of the soundgenerated by the liquefaction as well as possible, similar to thermalinsulation. It is equally preferred to subject the other components ofthe system to the sound insulation.

Alternatively, the sound insulation may also be configured to be active,in which case it would have, for example, a microphone for soundmeasurement, and would trigger, in response thereto, a soundcountereffect, such as to cause an outer liquefier wall etc. to vibratewith, e.g., piezoelectric means.

The embodiment shown in FIG. 3a is somewhat problematic in that theliquid 180 located within the liquefier will enter into the pipe 198,within which otherwise a compressed vapor is present, when the heat pumpis powered down. In one implementation, a backflow valve may be providedwithin line 198, for example near the output of the line from theliquefier. Alternatively, the line 198 may be directed upward,specifically so far upward that no liquid flows back into the compressorwhen the compressor is switched off. When the compressor is powered upagain, the water from the vapor line 198 will initially be pressed intothe liquefier by the compressed vapor.

Not until a sufficient portion of the water has been removed from theline 198 will a vapor be made to condensate within the liquefier. Anembodiment of such a type thus has a certain delay time which isnecessary until the water volume 180 is heated up again by thecompressed vapor. In addition, the work necessary for removing the waterwhich has entered into the line 198 from the line 198 again is no longerretrievable and is thus “lost” with regard to the heating system, suchthat small-scale losses in terms of the efficiency factor must beaccepted.

An alternative embodiment which overcomes this problem is shown in FIG.3b . Unlike in FIG. 3a , the compressed vapor is now not fed within apipe below the water level within the liquefier. Instead, the vapor is“pumped”, as it were, into the liquid within the liquefier from thesurface. For this purpose, the liquefier includes a nozzle plate 210comprising nozzles 212 which project in relation to the plane of thenozzle plate 210. The nozzles 212 extend below the water level of thewater volume 180 in the liquefier. The recessed portions between twonozzles, shown at 214 in FIG. 3b , by contrast extend above the waterlevel of the water volume 180 within the liquefier, so that the watersurface of the liquefier water, the water surface being interrupted by anozzle, is located between two nozzles. The nozzle 212 has nozzleopenings through which the compressed vapor which spreads from the line198 within the vapor volume 182 may enter into the liquefier water, asis schematically shown by arrows 216.

If, in the implementation of FIG. 3b , the compressor is powered down,this will result in that the liquid enters into the nozzles 212 of thenozzle plate 210 to a small extent only, so that very little work mustbe done in order to press the water out from the nozzles again when theheat pump is powered up again. At any rate, the expander 200 ensuresthat, due to being fed through the expander, the liquid transportedupward by the pump 202 is as cold as possible and comes into contactwith the warm vapor. Then the warm water will either immediately enterinto the advance flow 20 a, or it will spread within the water volumeover the expander edge, as is depicted by an arrow 218, so that atemperature stratification which is disturbed to as small an extent aspossible, in particular because of the shape of the expander, will occurwithin the liquefier outside the expander.

The flow rate present at the edge of the expander, i.e. where arrow 218is indicated, is considerably lower than in the center. It is preferredto operate the liquefier as a temperature layer storage such that theheat pump and, in particular, the compressor need not run withoutinterruption, but must run only when there is a need, as is also thecase for normal heating installations operating, for example, with anoil burner.

FIG. 3c shows a further preferred implementation of the liquefier in aschematic form. In particular, the liquefier comprises a gas separator220 coupled to the gas volume 182 within the liquefier. Any gas arisingwithin the liquefier, such as oxygen or another gas which may leakwithin the liquefier, collects within the gas-separator container 220.By actuating a pump 222, preferably at certain intervals, sincepermanent gas evacuation is not necessary due to the small quantity ofgas developing, this gas may then be pumped into the atmosphere.Alternatively, the gas may also be docked into the backflow 112 or 113of FIG. 2 again, so that the gas is again brought back into the groundwater reservoir, along with the ground water flowing back, where it willagain be dissolved within the ground water, or will merge into theatmosphere when it enters into the ground water reservoir.

Since the inventive system operates with water, no gases will develop,even with a high gas leakage, which have not already been dissolvedwithin the ground water previously, so that the gas separated offentails no environmental problems whatsoever. It shall again beemphasized that, due to the inventive dynamic-type compressorcompression and due to the use of water as the working fluid, there willbe no contamination or soiling by synthetic coolants or by oil, due toan oil cycle, at any point. As the working medium, the inventive systemat any point has water or vapor, which is at least as clean as theoriginal ground water, or is even cleaner than the ground water due tothe evaporation within the evaporator, since the water is distilledwater once the compressed vapor has been liquefied again within theliquefier.

In the following, a preferred embodiment of the evaporator will bedepicted with reference to FIG. 4a so as to advantageously employ theliquefier drain to accelerate the evaporation process. For this purpose,the drain, which, as one knows, has the temperature of the heatingsystem backflow, i.e. has a much higher temperature than the groundwater pumped from the earth, is passed through the expander 108 of theevaporator, so that the wall of the drain pipe 204 acts as a nucleus fornucleate boiling. Thus, a substantially more efficient vapor isgenerated by the evaporator than if no such nucleating action wereprovided. In addition, it is preferred to configure the wall of thedrain pipe 204, at least within the expander, to be as structured aspossible, as is depicted at 206, to improve the nucleation for thenucleate boiling even more. The rougher the surface of the drain pipe204, the more nuclei will be generated for nucleate boiling. It shall benoted that the flow through the drain pipe 22 is only very low, sincewhat is dealt with here is only the 4 ml per second which are fed to theliquefier in one mode of operation. Nevertheless, the considerably moreefficient nucleate boiling may be caused already with this small amountand because of the temperature, which is relatively high as compared tothe ground water, so as to reduce the size of the evaporator whilemaintaining the efficiency of the heat pump.

To accelerate the evaporation process, alternatively or additionally, anarea of the evaporator which has water which is to be evaporated locatedthereon, i.e. the surface of the expander or a part thereof, may beconfigured from a rough material to provide nuclei for nucleate boiling.Alternatively or additionally, a rough grate may also be arranged (closeto) below the water surface of the water to be evaporated.

FIG. 4b shows an alternative implementation of the evaporator. While thedrain in FIG. 4a has been employed merely as a “flow-through” assistanceof the nucleate formation for efficient evaporation, and, as has beendepicted on the left-hand side in the picture in FIG. 4a , the drain isdrained off once it has passed through the evaporator, the drain in FIG.4b is itself used for reinforcing the nucleate formation. For thispurpose, the liquefier drain 22 of FIG. 2 is connected to a nozzle pipe230, possibly via a pump 192 or, if conditions permit, without a pump,the nozzle pipe 230 having a seal 232 on one end and having nozzleopenings 234. The warm liquefier water drained from the liquefier viadrain 22 at a rate of, for example, 4 ml per second is now fed into theevaporator. On its way to a nozzle opening 234 within the nozzle pipe230, or immediately at the exit of a nozzle, it will already evaporate,as it were, below the water surface of the evaporator water because ofthe pressure which is too low for the temperature of the drain water.

The vapor bubbles forming there will immediately act as boiling nucleifor the evaporator water which is pumped via the inflow 102. Thus,efficient nucleate boiling may be triggered within the evaporatorwithout any major additional measures being taken, this triggeringexisting, similar to FIG. 4a , because of the fact that the temperaturenear the rough area 206 in FIG. 4a or near a nozzle opening 234 isalready so high that, given the existing pressure, evaporation willimmediately take place. This evaporation forces the generation of asmall vapor bubble which, if the conditions are favorably selected, willhave a very high probability of not collapsing again, but of developinginto a vapor bubble which goes to the surface and which, once it hasentered into the vapor volume within the evaporation chamber, will besucked off by the compressor via the suction pipe 12.

The embodiment shown in FIG. 4b necessitates the liquefier water to bebrought into the ground water cycle, since the medium exiting the nozzlepipe 230 eventually will re-enter into the backflow 112 via the overflowof the evaporator, and will thus be made to contact the ground water.

If there are water-regulatory provisions or any other reasons why thisis not admissible, the embodiment shown in FIG. 4c may be employed. Thewarm liquefier water provided by the liquefier drain 22 is introducedinto a heat exchanger 236 at a rate of, e.g., 4 ml per second to giveoff its heat to ground water which has been branched off from the mainground water stream within line 102 via a branch line 238 and abranching-off pump 240. The branched-off ground water will thenessentially take on the heat of the liquefier drain within the heatexchanger 236, so that pre-heated ground water is introduced into thenozzle pipe 230, for example at a temperature of 33° C. so as toeffectively trigger or support the nucleate boiling within theevaporator by means of the temperature which is high compared to theground water. On the other hand, the heat exchanger provides, via adrain line 238, drain water which is cooled to a relatively high extentand which is then fed to the sewage system via a drain pump 240. On thebasis of the combination of the branch line 238 and the branching-offpump 240 and the heat exchanger 236, only ground water is used in, orintroduced into, the evaporator without said ground water having been incontact with any other medium. Thus, there is no water-regulatoryrelevance associated with the embodiment shown in FIG. 4 c.

FIG. 4d shows an alternative implementation of the evaporator with edgefeeding. Unlike in FIG. 2, here the expander 200 of the evaporator isarranged below the water level 110 within the evaporator. This causeswater to flow toward the center of the expander “from outside” so as tobe returned in a central line 112. While the central line in FIG. 2 hasserved to feed the evaporator, in FIG. 4d it now serves to drain off thenon-evaporated ground water. By contrast, the line 112 shown in FIG. 2has served to drain off non-evaporated ground water. In FIG. 4d , bycontrast, this line at the edge serves as a ground water feed.

FIG. 4e shows a preferred implementation of the expander 200 as may beemployed within the evaporator, or of the expander as may also beemployed, e.g., within the liquefier and as is shown, for example, inFIG. 2 or FIG. 3a or 3 b, respectively. The expander is preferablyconfigured such that its small diameter preferably enters into theexpander in the center of the “large” expander area. This diameter ofthis inflow or drain (in FIG. 4d ) preferably ranges between 3 and 10 cmand, in particularly preferred embodiments, between 4 and 6 cm.

The large diameter d2 of the expander ranges between 15 and 100 cm inpreferred embodiments, and is smaller than 25 cm in particularlypreferred embodiments. The small configuration of the evaporator ispossible if efficient measures for triggering and assisting nucleateboiling are employed, as has been explained above. The small radius d1and the large radius d2 have an area of curvature of the expanderlocated between them which is preferably configured such that withinthis area a laminar flow results which is decreased from a fast flowrate, preferably within the range from 7 to 40 cm per second, to arelatively small flow rate at the edge of the expander. Largediscontinuities of the flow rate, for example eddies within the area ofthe line of curvature, or “bubbling effects” above the inflow, if theexpander is viewed from the top, are preferably avoided since they maypossibly have a negative effect on the efficiency factor.

In particularly preferred embodiments, the expander has a shape whichresults in that the height of the water level above the expander surfaceis smaller than 15 mm and is preferably between 1 and 5 mm. It istherefore preferred to employ an expander 200 configured such that inmore than 50% of the area of the expander, when viewed from the top, awater level exists which is smaller than 15 mm. Thus, efficientevaporation may be ensured across the entire area which is evenincreased, it terms of its efficiency, when measures for triggeringnucleate boiling are used.

Thus, the inventive heat pump serves to efficiently supply buildingswith heat, and it no longer necessitates any working substance whichnegatively affects the world climate. In accordance with the invention,water is evaporated under very low pressure, is compressed by one orseveral dynamic-type compressors arranged one behind the other, and isagain liquefied into water. The transported energy is used for heating.In accordance with the invention, use is made of a heat pump whichpreferably represents an open system. Here, open system means thatground water or any other available aqueous medium carrying heat energyis evaporated, compressed and liquefied under low pressure. The water isdirectly used as the working substance. Thus, the energy contained isnot transmitted to a closed system. The liquefied water is preferablyused directly within the heating system and is subsequently suppliedback to the ground water. To capacitively decouple the heating system,it may also be terminated by a heat exchanger.

The efficiency and usefulness of the present invention is represented bymeans of a numerical example. If one assumes an annual heatingrequirement of 30,000 kWh, in accordance with the invention aboutmaximally 3,750 kWh of electrical current must be expended for operatingthe dynamic-type compressor to achieve this, since the dynamic-typecompressor need only provide about an eighth of the entire amount ofheat necessary.

The eighth results from the fact that a sixth needs to be expended inthe event of extreme cold only, and that, for example, at transitiontemperatures such as in March or at the end of October, the efficiencyfactor may rise to a value of more than 12, so that, on average, amaximum of one eighth must be expended over the year.

At electricity prices of about 10 eurocents per kWh, which may bearrived at for electricity if one buys electricity for which the powerstation need not guarantee that operation will be free frominterruptions, this roughly corresponds to annual costs of 375 euros. Ifone wants to generate 30,000 kWh using oil, one would need about 4,000l, which would correspond to a price of 2,800 euros on the basis ofcurrent oil prices, which are very unlikely to fall in the future. Inaccordance with the invention, one can therefore save 2,425 euros perannum! In addition, it shall also be pointed out that in comparison withburning oil or gas for heating purposes, up to 70% of the amount of CO2released is saved by means of the inventive concept.

To reduce the manufacturing cost and also to reduce the maintenance andassembly costs, it is preferred to configure the housings of theevaporator, of the compressor and/or of the liquefier and also,particularly, the radial-flow wheel of the dynamic-type compressor, fromplastic, and in particular from injection molding plastic. Plastic iswell suited since plastic is corrosion-resistant with regard to water,and since, in accordance with the invention, the maximum temperaturesare preferably clearly below the deformation temperatures of employableplastics compared to conventional heating systems. In addition, assemblyis particularly simple since negative pressure is present within thesystem consisting of evaporator, compressor and liquefier. Thus,substantially fewer requirements are placed on the sealings since theentire atmospheric pressure assists in keeping the housings leak-proof.Also, plastic is particularly well suited since at no location in theinventive system are there high temperatures which would necessitate theuse of expensive special plastics, metal or ceramic. By means of plasticinjection molding, the shape of the radial-flow wheel may also beoptimized in any manner desired while being manufactured in a simplemanner and at low cost despite its complicated shape.

Depending on the circumstances, the inventive method may be implementedin hardware or in software. Implementation can be on a digital storagemedium, in particular a disk or CD, with electronically readable controlsignals which may interact with a programmable computer system such thatthe respective method is performed. Generally, the invention thus alsoconsists in a computer program product with a program code, stored on amachine-readable carrier, for performing the inventive method when thecomputer program product runs on a computer. In other words, theinvention may thus be realized as a computer program having a programcode for performing the method when the computer program runs on acomputer.

While this invention has been described in terms of several embodiments,there are alterations, permutations, and equivalents which fall withinthe scope of this invention. It should also be noted that there are manyalternative ways of implementing the methods and compositions of thepresent invention. It is therefore intended that the following appendedclaims be interpreted as including all such alterations, permutationsand equivalents as fall within the true spirit and scope of the presentinvention.

The invention claimed is:
 1. A heat pump comprising: an evaporator forevaporating water as a working liquid to generate a working vapor, theevaporator comprising an evaporation chamber and being adapted togenerate an evaporation pressure of less than 20 hPa within theevaporation chamber, so that the water will evaporate at temperaturesbelow 18° C.; a compressor coupled to the evaporator for compressing theworking vapor, the compressor being adapted to compress the workingvapor to a working pressure of more than 5 hPa above the evaporationpressure; and a liquefier for liquefying a compressed working vapor, theliquefier being adapted to output a heat which has been acquired duringthe liquefaction to a heating system, wherein the compressor comprises aplurality of dynamic-type compressors, the plurality of dynamic-typecompressors comprising a first dynamic-type compressor and a lastdynamic-type compressor, wherein the dynamic-type compressors of theplurality of dynamic-type compressors are arranged one behind the other,wherein the first dynamic-type compressor is configured to compress theworking vapor to an intermediate pressure, wherein the last dynamic-typecompressor is configured to compress the working vapor to the workingpressure, and wherein one or more heat exchangers are arrangeddownstream from the first dynamic-type compressor or a furtherdynamic-type compressor of the plurality of dynamic-type compressors,and wherein the one or more heat exchangers is configured to withdrawheat from the working vapor and to heat water with the heat withdrawn.2. The heat pump as claimed in claim 1, wherein the evaporator comprisesa gas separator adapted to remove at least part of a gas dissolved inthe water to be evaporated from the water to be evaporated, so that theremoved part of the gas is not sucked in by the compressor via theevaporation chamber.
 3. The heat pump as claimed in claim 2, wherein thegas separator is arranged to feed the removed part of the gas tonon-evaporated water so that the gas is transported off by thenon-evaporated water.
 4. The heat pump as claimed in claim 1, wherein atleast two dynamic-type compressors of the plurality of dynamic-typecompressors, which are arranged one behind the other compriseradial-flow wheels driven with rotational directions directed in amanner opposed to one another.
 5. The heat pump as claimed in claim 1,wherein at least two dynamic-type compressors of the plurality ofdynamic-type compressors are configured to be controlled independentfrom each other at least with regard to numbers of revolution, so thatthe at least two dynamic-type compressors are operable with differentnumbers of revolutions.
 6. The heat pump as claimed in claim 1, whereinat least one heat exchanger from the one or more heat exchangers isadapted to reduce the temperature of the working vapor to a temperature,at a maximum, which is higher than a temperature of the working vaporprior to a dynamic-type compressor of the plurality of dynamic-typecompressors connected preceding to the at least one heat exchanger. 7.The heat pump as claimed in claim 1, wherein at least one of the firstdynamic-type compressor and the last dynamic-type compressor is aradial-flow dynamic-type compressor comprising a radial-flow wheel whichcomprises a plurality of vanes extending from one or several inner radiito one or several outer radii, the vanes extending to the outside, withregard to the radial-flow wheel, from different radii of the radial-flowwheel.
 8. The heat pump as claimed in claim 7, wherein at least one vaneis arranged between two vanes extending to the outside, with regard tothe radial-flow wheel, from a radius, the at least one vane extending tothe outside, with regard to the radial-flow wheel, from a larger radius.9. The heat pump as claimed in claim 7, wherein the radial-flow wheelcomprises a base and a cover, and wherein at least one vane of theradial-flow wheel extends to the outside from a larger radius thananother vane being integrally connected both to the cover and to thebase.
 10. The heat pump as claimed in claim 1, wherein at least one ofthe first dynamic-type compressor and the last dynamic-type compressoris implemented as a turbo compressor comprising a radial-flow wheel, orwherein the heat pump comprises a controller configured for maintaininga target temperature within a heating circuit, wherein the controller isconfigured to control a number of revolutions of a dynamic-typecompressor being arranged upstream in a cascade, so that when a highertarget temperature is input into the controller, a number of revolutionsof the dynamic-type compressor arranged upstream in the cascade isincreased less than a number of revolutions of a dynamic-type compressorarranged downstream in the cascade.
 11. A heat pump comprising: anevaporator for evaporating water as a working liquid to generate aworking vapor, the evaporator comprising an evaporation chamber andbeing adapted to generate an evaporation pressure of less than 20 hPawithin the evaporation chamber, so that the water will evaporate attemperatures below 18° C.; a dynamic-type compressor coupled to theevaporator for compressing the working vapor, the compressor beingadapted to compress the working vapor to a working pressure of more than5 hPa above the evaporation pressure; and a liquefier for liquefying acompressed working vapor, the liquefier being adapted to output a heatwhich has been acquired during the liquefaction to a heating system,wherein the liquefier comprises a drain to drain off liquefied workingliquid, and wherein the drain to drain off liquefied working liquidcomprises a drain portion arranged within the evaporator, wherein thedrain portion is configured for providing a nucleating effect for abubble evaporation within the evaporator.